An example of a commercially available haemostatic locking clip is the Hem-o-lok ligating clip, available from Weck Closure Systems, USA. This clip takes the form of a hinged plastic jaw with cooperating snap-fit closure formations on the end of each of the two jaw members. The clip is applied onto a blood vessel via a simple pliers-like applicator which closes the open jaw members together across the blood vessel, until the jaw members snap together. The clip has no inherent self closing bias, and the application mechanism is crude in that each clip must be loaded manually and individually on the applicator, in the open condition. To actuate the loaded applicator, a surgeon must make available his whole dominant hand, because of the pliers-grip hand action required.
A permanent occlusion cerebral aneurysm clip is on the market from Aesculap, under the name of the Yasargil-Phynox aneurysm clip. This clip takes the form of a spring-hinged cobalt-chrome (or sometimes titanium) metal alloy jaw provided with a self closing spring bias. The clip is applied onto a cerebral blood vessel via a simple pliers-like applier which initially opens the jaw members against the spring bias, so that the open jaw can be applied across the blood vessel. The applier can then be released, so that the jaw members spring together. Again, this clip suffers from the disadvantages that each clip must be loaded manually and individually on the applier, in the open condition, and, to actuate the loaded applier, a surgeon must make available his whole dominant hand, because of the pliers-grip hand action required.
WO-A-00/35355, the disclosure of which is incorporated herein by reference, describes a surgical apparatus and method for occluding or encircling a body passageway, e.g., for haemostasis. The method involves offering a surgical clip formed from a temperature-dependent shape-memory material, to a blood vessel or other body passageway in a first clip configuration at a temperature below body temperature, and allowing the temperature of the clip to rise by the proximity of the body passageway to the clip. The rise in temperature assists the clip to deform into a second, occluding, configuration in which the clip is closed around the body passageway.
One particular clip design is shown in FIGS. 19 to 21 of this prior art. The clip comprises an elongate element formed of circular cross-section shape-memory metal (Nitinol) wire shaped to have generally first and second ends and a sinuously curved intermediate central portion. The first and second ends of the wire element form legs of the clip and the sinuously curved intermediate central portion forms two apices directed towards the legs, which provide shoulders to which the closing force of the legs in the second configuration is directed. In effect, the legs of the clip squeeze the body passageway against the apices of the central portion of the clip to provide occlusion of the body passageway.
It is found that there is still room for improvement of the occlusive effect of the prior art clips.